WebXR: Don't request hand-tracking feature by default.

[Mugen87]

Fixed #27698.

Description

This PR ensures VRButtons.createButton() gets the sessionInit parameter like XRButton and ARButton.

Besides, the optional feature hand-tracking is not requested by default anymore to avoid unnecessary permission prompts in visionOS.

/cc @cabanier

[cabanier]

Yes, this is fine

[Mugen87]

Noted this change in the migration guide for r162: https://github.com/mrdoob/three.js/wiki/Migration-Guide#r161--r162

[mrdoob]

But... How do we select/drag anything (create input events) on VisionOS if it's not with hand-tracking?

If we go into a WebXR session and we can't create any event... The only use case I can think of is watching a immersive video but we wouldn't even have controls for it.

[mrdoob]

Hmm, yeah... I guess in the handinput examples it should be requiredFeatures?

[Mugen87]

But... How do we select/drag anything (create input events) on VisionOS if it's not with hand-tracking? If we go into a WebXR session and we can't create any event... The only use case I can think of is watching a immersive video but we wouldn't even have controls for it.

/ping @m-blix

[cabanier]

But... How do we select/drag anything (create input events) on VisionOS if it's not with hand-tracking?

If we go into a WebXR session and we can't create any event... The only use case I can think of is watching a immersive video but we wouldn't even have controls for it.

That doesn't work on Vision Pro anyway since Safari doesn't create events for hands. I'm unsure why they made that decision but it's unlikely to change.
Instead, they added support for transient-pointer in VisionOS 1.1 which is now in beta. That works without WebXR Hands and lets you select with your eyes and hands. Quest Browser has a version of it behind a flag.

If you turn on WebXR hands on Vision OS 1.1, you may get 3 or 4 controllers (2 hands and 1/2 transient controllers). This is not supported by three at the moment since it only looks at the first 2 input sources.
I'm unsure if Quest browser will add support for this because regular controller input works better.

[mrdoob]

That doesn't work on Vision Pro anyway since Safari doesn't create events for hands. I'm unsure why they made that decision but it's unlikely to change. Instead, they added support for transient-pointer in VisionOS 1.1 which is now in beta. That works without WebXR Hands and lets you select with your eyes and hands. Quest Browser has a version of it behind a flag.

Sounds like we're going to have to rework all this 😔

[cabanier]

Sounds like we're going to have to rework all this 😔

I'm trying to clean up the spec so it's not as confusing but am getting pushback: immersive-web/webxr#1358 (comment)

[zalo]

Just stubbed my toe on Apple's transient-pointer stuff today with an OpenXR update I'm making to LeapShape:
https://zalo.github.io/LeapShape/

It's fine if they want their special transient pointers which work without hand tracking, but then they should also fire polyfilled events on the hands when they are granted so everybody else's apps aren't broken.

They even cited three.js as not supporting their just-invented "spec" in their FAQ instead of submitting any PRs to fix it:

When hand-tracking is enabled I can’t select anything.
Your experience probably is only looking at events which correspond to the first two inputs in the inputSources array. Many examples in the popular framework Three.js only act on events related to inputs at index 0 and 1. When hand tracking is enabled, the inputs corresponding to the hand tracking data appear in entries 0 and 1 but the transient-pointer style inputs appear in entries 2 and 3.

Identifying potential issues in existing WebXR scenes
WebXR is provided in visionOS 1.1 for testing purposes only. If you encounter bugs in the browser, please don’t attempt to target a user-agent string to work around them. Instead, report them to us via Feedback Assistant.

Hah! If you don't want workarounds, don't ship intentionally broken products and leave them that way for four months!

I'm going to look into submitting a PR later that explores polyfilling the missing input logic and perhaps adding a framerate up-interpolator for their janky 30hz tracking so hands work better in three.js than their own native apps.

I'm also thinking about contributing the PinchMoveControls from LeapShape to three.js as a more general camera/locomotion system (now that the camera parenting bug has been fixed...).

[mrdoob]

@zalo amazing stuff!